Evolution and systematics

Nearly a century ago, Ernst Hartert, Curator of the incredible Rothschild collection of preserved birds, observed: "What can't be classified is regarded as a babbling thrush." In the opinions of many of today's ornithologists, Hartert then proceeded to confuse matters further. The convoluted history of babbler classification is well treated in Sibley and Ahlquist's Phylogeny and Classification of Birds, and the reader is best referred to that book. Suffice it to say that exactly what a babbler is, and how it should be classified, has been, and remains, a controversy among ornithologists.

Jean Delacour's masterful arrangement of babblers, proposed in the 1940s and 1950s, has worked remarkably well, even as 1980s experiments in DNA-hybridization completely reorganized bird classification, and the rationale behind it. Delacour considered the babblers a vast subfamily, Timali-inae, one among many in the huge family Muscicapidae, created by Hartert in 1910, and now determined to be a hodgepodge of unrelated birds. Delacour divided his Timali-inae into a series of tribes, including one for both the wren-tit (Chamaea) and bearded reedling (Panurus), both of which were traditionally placed in different families. He also gave tribe status within the babblers to the parrotbills (Paradoxor-nis and Conostoma) and to the genus Picathartes. Picathartes had long been especially controversial, being assigned to the starling and crow families by various authorities.

The DNA research of Charles Sibley and his associates has led them to place the babblers in the family Sylviidae, together with many of the birds traditionally called Old World warblers. Within this family, they have divided the babblers into two subfamilies. Two genera, the laughing thrushes (Garru-

lax) and liocichlas (Liockhla), are given their own subfamily, Garrulacinae. The other babblers, including the parrotbills, which have traditionally been placed in a subfamily, Paradox-ornithinae (or Panurinae), are included by Sibley in the subfamily Sylviinae, divided into three tribes. All but one of these are in the tribe Timaliini, the exception being the wrentit, comprising its own tribe, Chamaeini. The third tribe, Sylvi-ini, consists of the warblers of the genus Sylvia, including such familiar European birds as the blackcap, whitethroats, and the garden warbler. One controversial inclusion in the tribe Timaliini, as Sibley defines it, is the genus Rhabdornis, the Philippine creepers, traditionally placed near the nuthatches and creepers. On the other hand, the genera Pomatostomus and Garritornis, considered by Delacour and others to be close relatives of the scimitar babblers, now constitute their own family, Pomatostomidae, which Sibley and colleagues placed near the crow family, Corvidae. The rail babblers (Eupetes and Ptil-orrhoa), which Delacour initially assigned to a tribe within the Timaliinae, then later considered a separate subfamily, are classified by Sibley as a subfamily within the Corvidae. It is not surprising that Sibley removed Picathartes, long a source of disagreement, from the Timaliinae, nor is his refusal to place their family in close proximity to any other. What is truly startling is his inclusion, in the family Picathartidae, of the rock jumpers (Chaetops), traditionally classified as thrushes (Turdidae).

Paleontology has, thus far, not served to clarify the origins and relationships of babblers, the only fossils being a Middle Pleistocene example of the modern species, the Arabian babbler (Turdoides squamiceps). DNA research seems to support Asian origins in the Oligocene, about 40 million years ago.